Epoxy compositions having improved impact resistance

Abstract

This invention relates to compositions useful as adhesives and more particularly to the preparation of heat-cured epoxy-based adhesive compositions with improved impact resistance and good adhesion to oily metal substrates.

1. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activiated latent curing agent; 
 additionally comprising at least one filler selected from the group consisting of platy fillers, hollow glass microspheres and combinations thereof. 
 
     
     
       2. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 additionally comprising at least one chelate-modified epoxy resin. 
 
     
     
       3. A composition of comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 comprising from about 0.1 to about 3 weight percent of at least one chelate-modified epoxy resin. 
 
     
     
       4. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 comprising at least one substituted guanidine heat-activated latent curing agent. 
 
     
     
       5. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 wherein said rubber particles have an average diameter of from about 25 to about 200 nm. 
 
     
     
       6. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 wherein the weight ratio of epoxy resin:combined weight of auxiliary impact modifier/toughener and rubber particles having a core-shell structure is from about 0.2:1 to about 3:1. 
 
     
     
       7. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 wherein the weight ratio of auxiliary impact modifier/toughener:rubber particles is from about 0.2:1 to about 5:1. 
 
     
     
       8. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 additionally comprising at least one reactive diluent which is a mono-epoxide. 
 
     
     
       9. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 comprising from about 25 to about 55 weight percent epoxy resin, from about 5 to about 40 weight percent auxiliary impact modifier/toughener, and from about 5 to about 25 weight percent rubber particles having a core-shell structure, wherein the weight ratio of epoxy resin:combined weight of auxiliary impact modifier/toughener and rubber particles having a core-shell structure is from about 0.2:1 to about 3:1 and the weight ratio of auxiliary impact modifier/toughener:rubber particles is from about 0.2:1 to about 5:1. 
 
     
     
       10. A composition comprising:
 A) at least one epoxy resin; 
 B) rubber particles having a core-shell structure; 
 C) at least one auxiliary impact modifier/toughening agent; 
 D) at least one heat-activated latent curing agent; 
 wherein at least a portion of the rubber particles having a core-shell structure have an average diameter of from about 25 to about 200 nm and are stably dispersed in a masterbatch comprised of epoxy resin when combined with the other components of the composition, with said rubber particles having a core comprised of a polymer or copolymer of 1,4-butadiene having a glass transition temperature of not greater than −40° C.